The present invention relates to a ventilation controlling apparatus and a method for controlling ventilation, particularly for feeding defrost and side window demist outlets in motor vehicles.
In motor vehicles at moderate outside temperatures (up to 25° C.) passengers usually prefer using the bi-level ventilation mode of a heating, ventilation and air conditioning (HVAC) unit. In this mode vent and floor outlets are at least partially open. When air humidity is high as it tends to be the case the more passengers are inside the side windows are prone to fog up. To keep passengers comfortable in this situation the side windows demist outlets have to be open while the defrost outlets remain closed. Otherwise there could emerge a fogged up spot on the outside of the windshield.
There are different approaches known for solving this problem. One is the usage of a film door inside the ventilation controlling apparatus as in US 2002/0197951 A1. A film door is a film which is moved by two coils, one of them spring loaded. The film has openings stamped out such that the cross sectional open area allows for air to flow through. A ventilation controlling apparatus with such a film door can easily be designed so it solves the aforesaid problem. The disadvantage is its need for space in order to package the two coils as well as the challenge to seal the moving film reliably.
Furthermore the sealing can lead to a wiping or scratching noise during operation which is annoying for the passengers.
Another approach as in DE 197 57 280 A1 uses moving doors or butterfly valves equipped with sealing foam wiping on a surface and thus keeping air from flowing to the defrost outlet while the synchronously turned door for the side window demist outlet is already open in this mode. However the wiping or scratching noise problem applies to this solution, too.